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Physical Activity Status, But Not Age, Influences Inflammatory Biomarkers and Toll-Like Receptor 4

¹ Department of Health and Human Performance, University of Houston, Texas.
² Wastl Human Performance Laboratory, Department of Health and Kinesiology, ³ Department of Foods and Nutrition, ⁴ Department of Statistics, and ⁵ Bindley Biosciences Center, Basic Medical Sciences, Purdue University, West Lafayette, Indiana.

Address correspondence to Brian K. McFarlin, PhD, University of Houston, Department of Health and Human Performance, 3855 Holman St., Houston, TX 77204. E-mail: bmcfarlin{at}uh.edu

Background. Chronic inflammation has been implicated in the development of cardiovascular disease, diabetes mellitus, cachexia, and osteoporosis. Regular physical activity has been purported to possess "anti-inflammatory" properties which may limit chronic inflammation. Recently, we hypothesized that toll-like receptor 4 (TLR4) may play a role in activity-induced modulation of inflammation. Therefore, the purpose of this study was to determine the association between age, physical activity status, biomarkers of inflammation, and TLR4.

Methods. Male and female participants (n = 84) were recruited to fill one of the following groups: young (18–30 years), active; young, inactive; old (60–80 years), active; or old, inactive. To assess physical activity status, participants completed a Paffenbarger Physical Activity Questionnaire and a modified Balke submaximal treadmill test. After grouping and screening, participants were given a standard mixed diet to consume 24 hours prior to arriving at the laboratory. Participants were instructed to consume all food by 10 PM the night prior to blood sampling (8-hour fast). Following 30 minutes of seated rest in a quiet room, venous blood samples were collected. Lipopolysaccharide-stimulated inflammatory cytokine production and plasma high-sensitivity C-reactive protein (hsCRP) were determined by enzyme-linked immunosorbent assay, and TLR4 expression was determined by flow cytometry.

Results. Lipopolysaccharide-stimulated interleukin-6, interleukin-1ß, and tumor necrosis factor- production, TLR4 expression, and hsCRP were significantly lower in active compared to inactive participants (p <.05). Also, older participants had significantly higher hsCRP than young participants had (p <.05).

Conclusions. The findings of the present study support previous reports which infer that acute exercise or a physically active lifestyle may possess anti-inflammatory properties. Also this study, along with previous work from our laboratory, suggests that TLR4 may play a role in regulating the link between inflammatory cytokine production and a physically active lifestyle.